View source for Harmonic Analysis of Current Velocity

[[de:Harmonische Analyse der Strömung]]
[[Category:Tidal Constituents]]

=Motivation=

For almost any location within an estuary the current velocity can be decomposed into a periodic part driven by the tides (astronomical and shallow water tides) as well as a non-periodic part driven by river runoff, meteorological effects as well as local topographic features.

[[File:Tidal_current_ellipse_definition.gif|200px|thumb|right|defintion of tidal ellipse]]
For each tidal constituent the tip of the current velocity vector describes an ellipse, the tidal ellipse (see accompanying figure). Within each period of the respective tidal constituent a full rotation is executed. Characteristic parameters for a tidal ellipse are semi major axis, semi minor axis, inclination of tidal ellipse as well as its eccentricity. In dependence on eccentricity the ellipse degenerates either to a circle (eccentricity +1.0 or -1.0) or a straight line (eccentricity 0.0). The beforementioned parameters are well suited to describe the tidal influence on current velocity.

=Basic Concepts=

Basic informations on  ''Tidal Harmonic Analysis'' are presented in [[Harmonic Analysis of Water Level]]. The methods used to compute various ellipse parameters using program [[NCANALYSE]] are described in more detail in publication [[File:zhigang_xu_2000_ellipse_parameters_conversion.pdf]].

=Definition of Characteristic Numbers=

====Residual Tidal Constituent Velocity (Vres)====
Residual value of current velocity (computed from harmonic analysis) within the period of data analysis.<br />
The residual is computed for permanently wet locations only.<br />
<!-- [[Example figures: residual current velocity (computed from harmonic analysis)]]. <br /> -->

==Amplitude of Tidal Constituent Velocity==

==Phase of Tidal Constituent Velocity==

==Error in Amplitude of Tidal Constituent Velocity==

==Error in Phase of Tidal Constituent Velocity==

==Semi Major Axis of Tidal Constituent Ellipse==

==Semi Minor Axis of Tidal Constituent Ellipse==

==Eccentricity of Tidal Constituent Ellipse==

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